AN ALGORITHM FOR REAL-TIME, CONTINUOUS EVALUATION OF LEFT-VENTRICULARMECHANICS BY SINGLE-BEAT ESTIMATION OF ARTERIAL AND VENTRICULAR ELASTANCE

We describe a computer algorithm that allows continuous, real-rime eva luation of ventricular elastance (Ees), arterial elastance (Ea), and t heir coupling ratio in a clinical setting. In the conventional pressur e-volume analysis of left ventricular (LV) contractility, invasive met hods of volume determination and a significant, rapid preload reductio n are required to generate Ees. With the help of automated border dete ction by transesophageal echocardiography, and a technique of estimati ng peak LV isovolumic pressure, Ea and Ees were determined from a sing le cardiac beat without the need for preload reduction. A comparison o f results obtained by a conventional approach and the new algorithm te chnique, showed good correlation for Ea (r = 0.86, p < 0.001) and Ees (r = 0.74, p = 0.001). Bias analysis showed a bias (d) of 1.47 mmHg/cm (2) for Ea with a standard deviation (SD) of 7.03 mmHg/cm(2), and uppe r (d+2SD) and lower (d-2SD) limits of agreement of 15.25 mmHg/cm(2) an d -12.31 mmHg/cm(2)?, respectively. Bias analysis showed a bias of -1. 42 mmHg/cm(2) for Ees with a SD of 4.88 mmHg/cm(2), and limits of agre ement of 8.15 mmHg/cm(2) and -10.98 mmHg/cm(2). The algorithm's stabil ity to artifacts was also analyzed by comparing magnitudes of residual s of Ea and Ees from source signals with and without noise. With Ea di ffering by an average of 1.036 mmHg/cm(2) and Ees differing by an aver age of 0.836 mmHg/cm(2), the algorithm was found to be stable to artif acts ill the source signals.